PHP 责任链模式讲解和代码示例

<?php namespace RefactoringGuru\ChainOfResponsibility\RealWorld; /** * The classic CoR pattern declares a single role for objects that make up a * chain, which is a Handler. In our example, let's differentiate between * middleware and a final application's handler, which is executed when a * request gets through all the middleware objects. * * The base Middleware class declares an interface for linking middleware * objects into a chain. */ abstract class Middleware { /** * @var Middleware */ private $next; /** * This method can be used to build a chain of middleware objects. */ public function linkWith(Middleware $next): Middleware { $this->next = $next; return $next; } /** * Subclasses must override this method to provide their own checks. A * subclass can fall back to the parent implementation if it can't process a * request. */ public function check(string $email, string $password): bool { if (!$this->next) { return true; } return $this->next->check($email, $password); } } /** * This Concrete Middleware checks whether a user with given credentials exists. */ class UserExistsMiddleware extends Middleware { private $server; public function __construct(Server $server) { $this->server = $server; } public function check(string $email, string $password): bool { if (!$this->server->hasEmail($email)) { echo "UserExistsMiddleware: This email is not registered!\n"; return false; } if (!$this->server->isValidPassword($email, $password)) { echo "UserExistsMiddleware: Wrong password!\n"; return false; } return parent::check($email, $password); } } /** * This Concrete Middleware checks whether a user associated with the request * has sufficient permissions. */ class RoleCheckMiddleware extends Middleware { public function check(string $email, string $password): bool { if ($email === "admin@example.com") { echo "RoleCheckMiddleware: Hello, admin!\n"; return true; } echo "RoleCheckMiddleware: Hello, user!\n"; return parent::check($email, $password); } } /** * This Concrete Middleware checks whether there are too many failed login * requests. */ class ThrottlingMiddleware extends Middleware { private $requestPerMinute; private $request; private $currentTime; public function __construct(int $requestPerMinute) { $this->requestPerMinute = $requestPerMinute; $this->currentTime = time(); } /** * Please, note that the parent::check call can be inserted both at the * beginning of this method and at the end. * * This gives much more flexibility than a simple loop over all middleware * objects. For instance, a middleware can change the order of checks by * running its check after all the others. */ public function check(string $email, string $password): bool { if (time() > $this->currentTime + 60) { $this->request = 0; $this->currentTime = time(); } $this->request++; if ($this->request > $this->requestPerMinute) { echo "ThrottlingMiddleware: Request limit exceeded!\n"; die(); } return parent::check($email, $password); } } /** * This is an application's class that acts as a real handler. The Server class * uses the CoR pattern to execute a set of various authentication middleware * before launching some business logic associated with a request. */ class Server { private $users = []; /** * @var Middleware */ private $middleware; /** * The client can configure the server with a chain of middleware objects. */ public function setMiddleware(Middleware $middleware): void { $this->middleware = $middleware; } /** * The server gets the email and password from the client and sends the * authorization request to the middleware. */ public function logIn(string $email, string $password): bool { if ($this->middleware->check($email, $password)) { echo "Server: Authorization has been successful!\n"; // Do something useful for authorized users. return true; } return false; } public function register(string $email, string $password): void { $this->users[$email] = $password; } public function hasEmail(string $email): bool { return isset($this->users[$email]); } public function isValidPassword(string $email, string $password): bool { return $this->users[$email] === $password; } } /** * The client code. */ $server = new Server(); $server->register("admin@example.com", "admin_pass"); $server->register("user@example.com", "user_pass"); // All middleware are chained. The client can build various configurations of // chains depending on its needs. $middleware = new ThrottlingMiddleware(2); $middleware ->linkWith(new UserExistsMiddleware($server)) ->linkWith(new RoleCheckMiddleware()); // The server gets a chain from the client code. $server->setMiddleware($middleware); // ... do { echo "\nEnter your email:\n"; $email = readline(); echo "Enter your password:\n"; $password = readline(); $success = $server->logIn($email, $password); } while (!$success); 

Enter your email: asd Enter your password: 123 UserExistsMiddleware: This email is not registered! Enter your email: admin@example.com Enter your password: wrong UserExistsMiddleware: Wrong password! Enter your email: admin@example.com Enter your password: letmein ThrottlingMiddleware: Request limit exceeded! Enter your email: admin@example.com Enter your password: admin_pass RoleCheckMiddleware: Hello, admin! Server: Authorization has been successful!